Composite Materials Manufacturing Composite Materials Manufacturing 정분방

Introduction Definition: a material composed of 2 or more constituents Reinforcement (e.g., Fibers) matrix (e.g.,epoxy) Advantages High strength and stiffness Low weight ratio Material can be designed in addition to the structure Can manufacture structures and eliminate joints

Applications Aerospace industry Sporting goods Automotive Construction

Costs of composite manufacture Material costs -- higher for composites Constituent materials (e.g., fibers and resin) Processing costs -- embedding fibers in matrix Design costs -- lower for composites Can reduce the number of parts in a complex assembly by designing the material in combination with the structure

Material Forms and manufacturing Objectives of material production assemble fibers impregnate resin shape product cure resin

Sheet Molding Compound (SMC) Chopped glass fiber added to polyester resin mixture

Manufacturing - Filament Winding Highly automated low manufacturing costs if high throughput e.g., Glass fiber pipe, sailboard masts the only manufacturing technique suitable for making certain specialized structures, such as pressure vessels.

Prepregs Prepreg and prepreg layup “prepreg” - partially cured mixture of fiber and resin Unidirectional prepreg tape with paper backing  wound on spools  Cut and stacked Curing conditions Typical temperature and pressure in autoclave is C, 100 psi

Manufacturing - Layups compression molding vacuum bagging

Autoclave Autoclave Limitations labor intensive, high labor cost Advantages good for building prototype parts and small quantity runs

Resin transfer molding (RTM) Dry-fiber preform placed in a closed mold, resin injected into mold, then cured High cost, tooling design is complex

Manufacturing - Pultrusion Fiber and matrix are pulled through a die, like extrusion of metals -- assembles fibers, impregnates the resin, shapes the product, and cures the resin in one step. Example:Fishing rods Advantages: simple low-cost, continuous, and automatic process. Limitations: the axial direction, fiber angles 0°, not suit for tapered and complex shapes

Pultrusion

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